A Chitosan-Multiwall Carbon Nanotube Modified Electrode for Simultaneous Detection of Dopamine and Ascorbic Acid

Abstract

Dopamine (DA) is a very important neurotransmitter in the mammalian central nervous system. Because low levels of DA have been found in patients with Parkinson's disease, 1 its detection with high selectivity and sensitivity is of great significance in investigating its physiological functions and the diagnose of nervous diseases resulting from an abnormal metabolite. When solid electrodes are used to detect DA, the main and foremost difficulty is the interference of ascorbic acid (AA), which is oxidized at almost the same potential as DA.2 It is thus very important to develop an electrochemical method of high selectivity and sensitivity for the determination of DA.Chitosan, which is derived from chitin, has excellent biologic compatibility and can be used as a modifier because it has many amino and hydroxyl groups.3-8 Besides, using a natural polymer as a dispersant is a requirement of environment protection. Carbon nanotubes have attracted much attention because they have the ability to promote electron transfer reactions when used as electrode materials, 9,10 but carbon nanotubes are very stable and insoluble in most solvents, which restrained its application in electroanalysis. Thus, in this study, a multiwall carbon nanotube (MWNT)-chitosan modifier was obtained by putting MWNT into a chitosan solution (0.5%). The MWNTchitosan modified electrode (MC/GCE) has many advantages with regard to a low detection limit, a fast response, excellent reproducibility for the detection for DA and AA simultaneously. Experimental ApparatusAll of the electrochemical measurements were carried out with a bioanalytical system CV-50W electrochemical analyzer. The three-electrode system consisted of a modified GCE, a saturated calomel reference electrode (SCE), and a platinum auxiliary electrode. All potentials were referred to the SCE. The transmission electron microscopy image was done with a TEM-100CXII. ReagentsDopamine, ascorbic acid (Fluka Corp.). A chitosan solution (0.5%) was prepared by dissolving 0.05 g of chitosan in 10 ml acetic acid (2 mol l -1 ). 11 The MWNT used in this work (obtained from the Institute of Nanometer, Central China Normal University) was synthesized by catalytic pyrolysis and purified followed the method given in a reference. 12 Preparation for a MWNT-chitosan modified electrodeUpon putting 1 mg of MWNT into 5 mL of a chitosan solution (0.5%), ultrasonic agitation for a few minutes gave 0.2 mg ml -1 of a black suspension. Before being modified, the GCE was polished with 0.3 µm and 0.05 µm aluminum slurry, rinsed thoroughly with redistilled water, then ultrasonically rinsed with alcohol, redistilled water for 1 min each, and dried under an infrared lamp. After the GCE was cooled, it was smeared evenly with 10 µl of a MWNT-chitosan (0.5%) solution by a micro-syringe, and then dried under an infrared lamp for 10 min. After cooling, the MC/GCE could be used. Experimental procedureA 0.1 mol l -1 phosphate buffer solution (pH = 7.2) was used as the supporting electrolyte for the determination of DA and AA...

Application and Preparation of Chitosan Electrochemical Sensor

“…This sensor can determine L-ascorbic acid by method of semi differential voltammetry. Jiang [36] et al reported a modified electrode based on a chitosan multiwall carbon nanotube coated glassy carbon electrode is described, which exhibits an excellent sensitivity to determine dopamine and ascorbic acid simultaneously. Yang and Wei [37] reported a β-cyclodextrin multiwalled carbon nanotubes/chitosan modified electrode was prepared by layers by layer self assembly technique.…”

Electrochemical sensors based on carbon nanotubes and their use in biomedical research.Part 2: sensors manufactured by dispersion of carbon nanotubes by means of polyethyleneimine, organic dyes, cyclodextrins, chitosan, proteins, room-temperature ionic liquids, gels, and thiols. Sensors manufactured by dispersion of carbon nanotubes by electropolymerization process. sensors manufactured by dispersion of carbon nanotubes by layer-by-layer deposition

“…Технологии изготовления электрохимических сенсоров путём нанесения углеродных нанотрубок на рабочую поверхность электрода с помощью полиэтиленимина [2][3][4][5][6][7], органических красителей [9,[11][12][13] и циклодекстринов [14][15][16][17] схожи между собой: нанотрубки распределяются в растворах перечисленных химических соединений, образуя гомогенную суспензию, которая далее наносится на поверхность электрода с последующим высыханием. Хитозан [18][19][20][21][22], белковые соединения [23,24], ионные жидкости [25,26], гели [27,28] и тиолы [29][30][31] также могут использоваться для нанесения углеродных нанотрубок на рабочую поверхность стеклоуглеродного, золотого или др. электрода.…”

“…Получаемые сенсоры позволяют определять большое число химических соединений, являющихся характерными для биомедицинских исследований, в частности дофамин [2-4, 11, 15, 19, 26, 43], допак [2,4], адреналин [4,15,35], норадреналин [4,17,20], аскорбиновая [2,7,19] и мочевая [16,20] кислоты, пероксид водорода [2,4,5,22,25,[27][28][29][36][37][38], NADH [21,44], глюкоза [2,21,22,28,29,[36][37][38][39]44], фруктоза [44], холестерин [27], цитохром с [30], амитрол [4,5], диурон [5], монурон [5], хлортолурон [5], офлоксацин [12], эстрадиол [13], тимин …”

“…В фосфатном буферном растворе (0,1 моль/л, рН 7,2) сигнал, обусловленный присутствием дофамина, наблюдался при электрическом потенциале +144 мВ, а аскорбиновой кислоты -при потенциале -29 мВ относительно электрического потенциала насыщенного каломельного электрода. Сигналы линейно зависели от концентраций названных химических соединений в диапазоне от 5×10 -7 до 1×10 -4 моль/л (дофамин) и от 5×10 -6 до 1×10 -3 моль/л (аскорбиновая кислота) [19]. Для определения мочевой кислоты и норадреналина Lu и др.…”

Carbon Nanotube-Based Cholinesterase Biosensors for the Detection of Pesticides

“…Chitosan (CHIT) displays excellent film-forming ability, high water permeability, good adhesion, and susceptibility to chemical modifications due to the presence of reactive amino and hydroxyl functional groups. The stable dispersion of CNTs was prepared in the acidic aqueous solutions of CHIT with the help of sonication (Jiang et al, 2004). It was demonstrated that CHIT might be adsorbed onto CNTs and form a special CHIT-CNT system, which can be precipitated from the solutions by the addition of concentrated salts or the adjustment of solution acidity.…”